The strange fact of the matter is that conservatives seem incapable of critiquing Marx.
But we have criticized Marx here from the left, granting the value of much of his discursive thinking but pointing to the problems with his theories. Marx was too immersed in the flush of scientific success in the physical sciences and thus prone to the tendency to think the social sciences needed a similar kind of science. Every attempt in that direction failed and Marx is no exception. The theory of historical materialism is dead weight now and yet obsessively defended mostly in vain. The confusion of the labor theory of value is another needless black hole of bad theory based on a core insight that would have thrived if it had never been turned into theory.
The left is not going to win these arguments, except with themselves, and move on to create socialism.